This invention relates generally to apparatus for lifting and towing disabled vehicles, particularly large vehicles such as dump trucks, buses, trailer cabs with a conventional fifth wheel coupler, or the like. Most commonly used for this purpose are specialized, heavy duty tow trucks or wreckers, such as those illustrated in U.S. Pat. Nos. 4,384,817, 4,473,334, and 4,611,968.
A trucking firm commonly operates with a fleet of trailers and a number of trailer cabs having a fifth wheel coupler by which the cab couples to and pulls a trailer. Those cabs often become disabled while on the road and must be towed back to a central service center for repair. Most firms, particularly smaller firms, cannot afford the luxury of owning their own wrecker because of its high cost and singular utility. Consequently, they must rely on an independent towing operator to tow the disabled cab in from its field location, sometimes from a significant distance at a substantial cost.
It would be advantageous for a trucking firm to be able to readily adapt one of its conventional cabs for additional use as a tow truck. Removable towing attachments have been purposed in the past, as exemplified by the constructions shown in U.S. Pat. Nos. 3,667,630, 4,000,823, and 4,383,792. However, units such as these are usually intended for use on lighter duty pick-up trucks for towing automobiles, and are unsuitable for usage with heavy duty vehicles. Another proposal shown in U.S. Pat. No. 4,152,006 permanently mounts a lifting boom at the rear of a cab having a conventional fifth wheel coupler, but that construction also has restricted application because the manner in which it may grasp and hold a disabled vehicle is severely limited. U.S. Pat. No. 4,152,006 also refers to detachable units, but discloses no specific structural details.